Please help us help you and fill where relevant:
Your LimeSurvey version: 6.4.10
Own server or LimeSurvey hosting: Own Server (IIS/MSSQL)
Survey theme/template:
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We have a 2.5 version of Lime running on a server we're trying to retire.  I have a Windows 2019 server running with IIS, including PHP 8.3.2 and LimeSurvey 6.4.10 installed.  When I access the LimeSurvey folder through the browser, it prompts me to start the installation.  All the pre-checks pass with minimum or exceeds requirements.  However, once I get to the database page, it never connects correctly.  We would like to just use the old database but are willing to create a new one.  The database login is a MSSQL login account that is still functioning for our old version surveys.  In the installer, it doesn't seem to be even attempting to connect (nothing shown in database logs, even with bad credentials entered).  It never finds the old database, and when I say to create one it always shows as failed and suggests checking credentials.  No attempts to create are logged in the SQL Server.  The database is on a custom port but we have tried all of the following with no noticeable change:

servername
servername:port
servername,port (this is how it looks on the old server config.php)
servername.domain.local
servername.domain.local:port
servername.domain.local,port
IPaddress
IPaddress:port
IPaddress,port

Any help would be appreciated.  Is there something specific that I needed to do in IIS to set this up?  The installer just started running when the LimeSurvey folder was put in the default site location.  I don't think we did any customization to it in IIS, and nothing in PHP beyond enabling all the required add-ons.  I know we don't have any internal firewall blocks between the IIS server and the DB server because we have other apps running on that IIS install that talk to the database just fine.  Is there any way that I can bypass the browser installation and just configure it manually?  

Is the PDO database driver installed?

PDO database driver for MySQL (pdo_mysql or pdo_mysqli) or Postgres (pdo_pgsql) or MSSQL (pdo_sqlsrv for Windows and pdo_dblib for Linux).

manual.limesurvey.org/Installation_-_Lim...rvey_on_your_website

Yes, the PDO_SQLSRV is installed and detected by the installer.
 

I have this issue with MSSQL : bugs.limesurvey.org/view.php?id=19387

Maybe related ?

That does sound like it could be the source of my issue. Is there any workaround for it, since the bug report has not been resolved yet?

Add your comments to the bug. More movement, more likely to get fixed.

Currently ; i add manually the needed part at github.com/LimeSurvey/LimeSurvey/blob/6d...rConfigForm.php#L584

It's a one time hack.